1. Technical Field
The present invention relates to a component holding head for use, e.g., in mounting electronic components on electronic circuit boards, a component mounting apparatus equipped with the component holding head, and a component hold method carried out by the component mounting apparatus.
2. Background Art
A component suction head part set in a component mounting apparatus adapted to automatically mount electronic components onto electronic circuit boards has nozzles to suck and mount the electronic components to the electronic circuit boards. Lately, precise control of the nozzles coming into contact with electronic components during sucking and mounting of the electronic components is considered as one of factors to improve quality of the electronic circuit boards to be produced. An example of the conventional electronic component mounting apparatus will be described with reference to FIG. 4.
FIG. 4 shows a component suction head part 101 including the aforementioned nozzles, a sucking device 103 for sucking the electronic components with the use of the nozzles, an X-Y robot 102 moving the head part 101 in X, Y directions, and a control device 104 controlling operations of the head part 101, the X-Y robot 102, and the sucking device 103 in the conventional electronic component mounting apparatus. The head part 101 is constructed as will be described below. Only essential parts constituting the head part 101 are indicated in FIG. 4 and, for instance, a body part of the head part 101 and the like are not illustrated. Reference numeral 135 in FIG. 4 is a spline shaft which has a nozzle 136 set at one end part 135a for sucking an electronic component 138 through a suction action, and a rotation receiver 143 at the other end part 135b. The suction action is conducted by the sucking device 103, whereby the air is guided into the sucking device 103 through the nozzle 136 and the spline shaft 135. Two nuts 131, 134 are fitted to the spline shaft 135 in an axial direction of the spline shaft 135 to make the spline shaft 135 slidable in the axial direction. These nuts 131, 134 are held to the body part (not shown) of the head part 101 via respective bearings 132, 133. The spline shaft 135 is accordingly rendered movable in the axial direction and rotatable in a circumferential direction relative to the body part.
The rotation in the circumferential direction of the spline shaft 135 is achieved by a motor 142. Specifically, a pulley 139 rotating along with the spline shaft 135 is fitted to the spline shaft 135. The spline shaft 135 is movable in the axial direction relative to the pulley 139. A pulley 141 is attached to a driving shaft of the motor 142 and is coupled to the pulley 139 via a belt 140. When the motor 142 rotates the pulley 141, the spline shaft 135 is accordingly rotated in the circumferential direction via the belt 140 and the pulley 139.
Meanwhile, the movement in the axial direction of the spline shaft 135 is caused by a motor 149. More specifically, a nut 146, whereat a lever 147 projects, is meshed with a ball screw 145 connected to a driving shaft of the motor 149 via a coupling 148. A roller 144 at a leading end of the lever 147 is engaged with a groove 143a formed in the rotation receiver 143. When the ball screw 145 is rotated by the motor 149, the lever 147 moves in the axial direction while the roller 144 is engaged with the rotation receiver 143, thereby moving the spline shaft 135 in the axial direction.
The conventional component mounting apparatus of the above constitution operates in the following manner.
When the X-Y robot 102 operates under the control of the control device 104, the head part 101 is moved to a component suction position where the electronic component is to be sucked. The motor 149 is driven under the control of the control device 104, thereby lowering the spline shaft 135 and the nozzle 136. At the same time, the sucking device 103 is driven to make the nozzle 136 suck the electronic component. Subsequently, the ball screw 145 is rotated backward by the motor 149 to raise the nozzle 136. In order to correct a mount direction of the sucked electronic component, the motor 142 is driven through the control action of the control device 104 to rotate the nozzle 136 to a proper position. The X-Y robot is driven again to move the head part 101 to a component mount position above the electronic circuit board, and then the motor 149 is driven to lower the nozzle 136. The electronic component 138 is thus mounted on the electronic circuit board.
The above-described constitution of the conventional component mounting apparatus has drawbacks, though.
In these days, the component mounting apparatus is adapted to handle not only electronic components, in which silicon substrates having electronic circuits formed thereon are sealed with resin material, but bare ICs and the like. In the case of bare ICs, a mount pressure by the nozzle 136 to the bare ICs at the time of mounting is required to be controlled to prevent damage to the bare ICs. Therefore, the component mounting apparatus is constituted to correctly manage a position of the nozzle 136 relative to the bare ICs in X, Y directions, and also to manage the pressure of the nozzle 136 on the bare ICs on the basis of a torque of the motor 149 moving the nozzle 136 up and down. Although a sensor is preferred to be directly installed at the nozzle 136 in the component mounting apparatus to correctly measure the position of the nozzle 136 in the X, Y directions and an up-down direction, it is impossible to set the sensor to the spline shaft which moves in the axial direction and the circumferential direction as described above. As such, the position of the nozzle 136 in the up-down direction is actually controlled on the basis of output information from a rotary encoder 150 incorporated in the motor 149.
On the other hand, the position of the spline shaft 135 in the axial direction is hard to correctly grasp, because the movement of the spline shaft 135 in the axial direction is carried out via the rotation receiver 143 and the roller 144, etc., which is dependent on movement accuracy of the ball screw 145 in the axial direction. Moreover, the rotation receiver 143 and the roller 144, etc. are formed of non-rigid material. Under the circumstances, the conventional electronic component mounting apparatus finds difficulty in accurate control of the movement of a leading end of the nozzle, resulting in an impediment to improvement of mount quality.
The present invention is devised to solve the aforementioned drawbacks and has for its object to provide a component holding head, a component mounting apparatus equipped with the component holding head, and a component hold method executed by the component mounting apparatus, which can improve mount quality of components to articles to which the components are to be mounted.
In accomplishing this and other objects, the present invention is constituted as described below.
According to a first aspect of the present invention, there is provided a component holding head equipped with a shaft which has a nozzle, for holding a component, set at one end part of the shaft and is driven in an axial direction thereof A magnet is fixed to a circumferential face of the shaft and a coil is disposed around the magnet, thereby constituting a voice coil motor for driving the shaft in the axial direction, so that movement of the shaft in the axial direction is controlled through control of power supply to the voice coil motor.
According to a second aspect of the present invention, there is provided a component holding head according to the first aspect, further comprising a detecting device which is installed at the shaft for detecting the movement of the shaft in the axial direction, so that an amount of the movement of the shaft in the axial direction by the voice coil motor is controlled on the basis of a detection result of the detecting device.
According to a third aspect of the present invention, there is provided a component holding head according to the second aspect, wherein the detecting device comprises a member to be detected which extends concentrically with the shaft. The member is directly fitted to the other end part of the shaft and moves in the axial direction in accordance with the movement of the shaft in the axial direction. The detecting device also includes a sensor for detecting movement of the member to be detected.
According to a fourth aspect of the present invention, there is provided a component holding head, according to the third aspect, wherein the member to be detected is a magnetic scale, and the component holding head further comprises a transmission sensor set in a noncontact state to detect presence/absence of blockage of light by a leading end of the magnetic scale, thereby detecting an origin position of the movement of the shaft.
According to a fifth aspect of the present invention, there is provided a component holding head according to the second aspect, wherein the detecting device comprises a sensor which is directly set at the other end part of the shaft via a bearing so as to be prevented from rotating together with the shaft when the shaft is driven in a circumferential direction, while being allowed to move in the axial direction in accordance with the movement of the shaft in the axial direction. The detecting device also includes a member to be detected by the sensor which extends parallel to the axial direction of the shaft.
According to a sixth aspect of the present invention, there is provided a component mounting apparatus for mounting components, which is equipped with the component holding head according to any one of the first through fifth aspects.
According to a seventh aspect of the present invention, there is provided a component mounting apparatus according to the sixth aspect, further comprising a detecting device which is set at the shaft to detect the movement of the shaft in the axial direction. The component mounting apparatus further includes a control device which controls an amount of the movement of the shaft in the axial direction caused by the voice coil motor on the basis of a detection result of the detecting device.
According to an eighth aspect of the present invention, there is provided a component mounting apparatus according to either the sixth aspect or the seventh aspect, wherein the shaft is movably arranged relative to a casing of the voice coil motor, with a nozzle suction pipe installed at the casing. An opening, communicating with a through hole or passage in the shaft, penetrates the shaft to communicate with the nozzle and opens into the casing, whereby the nozzle suction pipe and the opening are communicated with each other via the interior of the casing.
According to a ninth aspect of the present invention, there is provided a component hold method which is carried out with the use of a component holding head having a shaft which is equipped with a nozzle, for holding a component, at one end part of the shaft and is driven in an axial direction thereof. A magnet is fixed to a circumferential face of the shaft and a coil is arranged around the magnet, thereby constituting a voice coil motor for driving the shaft in the axial direction.
The method comprises detecting the movement of the shaft in the axial direction, caused by the voice coil motor, by a detecting device installed at the shaft, and further comprises controlling power supply to the voice coil motor on the basis of a detection result of the detecting device, thereby controlling a movement amount of the shaft in the axial direction to hold the component.
According to a tenth aspect of the present invention, there is provided a component hold method according to the ninth aspect, wherein a magnetic scale, which is a member to be detected of the detecting device, is provided along with a transmission sensor that is set in a state without contacting the magnetic scale. The transmission sensor detects presence/absence of blockage of light by a leading end of the magnetic scale 28, thereby detecting an origin position of the movement of the shaft.